This invention relates generally to locomotives and other off-highway vehicles, and more particularly to monitoring of sand levels carried therein.
Off-highway vehicles, particularly locomotives, use sand to increase wheel to rail adhesion and prevent wheel slip during adverse weather conditions such as rain, snow and ice. Sand is either applied manually by the locomotive operator with the push of a button or in some cases, a locomotive control system (LCS) has the ability to apply sand automatically if it detects a wheel slip on any of the locomotive axles. The dry sand is typically stored in four sand reservoirs on the locomotive, two located in the front and two in the rear. The two front sand reservoirs supply sand to the wheels located on the front locomotive truck while the rear sand reservoirs supply sand to the wheels located on the rear locomotive truck. The sand level in the reservoirs is normally checked whenever the locomotive is fueled. Checking the sand level in each of the locomotive sand reservoirs is currently a manual process which requires someone to open the fill lid on each of the locomotive sand reservoirs and check the actual level. The fill lids are typically located high on the locomotive car body thus making access difficult and dangerous for the operator and railroad maintenance personnel.
As part of the pre-departure checklist the locomotive operator will verify the delivery of sand to the wheels. The locomotive operator manually activates the sand system and performs a visual check to verify that sand is actually exiting from the locomotive sand pipes. This procedure only verifies operation of the locomotive sand system at the time of test. The operator and railroad maintenance personnel do not have any way of knowing if one or more of the locomotive sand reservoirs is at or near exhaustion. To compound matters, the sand system on a locomotive is not supervised. Once underway there is no safe and convenient method to verify the sand level in the sand reservoirs. Sand application is indicated when the sand button is depressed regardless of actual sand delivery. This is true even if all sand reservoirs are completely empty or the sand control system malfunctions.
There are many external sources that influence the amount of sand applied by the locomotive sand system. The consistency and moisture content of the sand, temperature and relative humidity, mechanical problems with the sand reservoir and its control mechanisms all influence sand consumption. Because of these inconsistencies, sand is not consumed equally from each of the sand reservoirs. Therefore the sand level in each of the sand reservoirs can vary greatly.
Sand is one of the most-consumed commodities on a railroad, second only to fuel. In order for the railroads to maintain a high level of operating efficiency, sand must be available for the operator and the LCS to apply at all times. The application of sand to the locomotive wheels helps to control wheel slip and increases locomotive adhesion thus avoiding an unwanted power reduction that can cost the railroad time and money. Sand is also applied to the locomotive wheels during an emergency stop condition. Even on dry rails, the application of sand under these conditions will increase locomotive adhesion thus helping to avoid wheel slips and stopping the train in the shortest amount of distance possible.